NOTE: One topic I did not cover is that some spirits can be obtained ONLY through the shops (ex. Fire Flower spirit)!
Timestamps:
World of Light 100%: 1:42
Classic Mode: 3:21
Shop (Using Gold): 4:41
Spirit Board: 5:43
Inventory Spirit List: 8:43
Inventory Items: 11:36
Summon: 13:44
Level Up/Enhancing: 16:15
Activities: 18:26
Shopping (Using SP): 20:20

In this video I detail how to quickly obtain all of the 1,297 spirits found in Super Smash Bros. Ultimate!

**About 2 days after this video was created, I successfully completed my goal of earning all of the spirits!